The OAK (Osteo-Arthritis Knee) polycentric orthotic knee joint is engineered to provide motion that better approximates normal physiologic knee movement for use in a custom Osteoarthritic Knee Orthosis. Unlike simple pivot knee joints, the polycentric action of the OAK provides inherent stability at full extension and easy gliding during swing phase. This allows the patient to feel the “glide flex” stability during the first 5° of flexion. This flexion is dynamically adjustable, with extension stops to meet rehabilitative demands. The OAK Orthosis is available with Comfil thermoformable composite materials that can be custom fit with a heat gun for increased comfort and support.